// ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
/*============================================================
** 
** Class:  Comparer 
**
** <OWNER>[....]</OWNER> 
**
**
** Purpose: Default IComparer implementation.
** 
**
===========================================================*/ 
namespace System.Collections { 

    using System; 
    using System.Globalization;
    using System.Runtime.Serialization;
    //using System.Security.Permissions;
    using System.Diagnostics.Contracts; 

    //[Serializable] 
[System.Runtime.InteropServices.ComVisible(true)] 
    public sealed class Comparer : IComparer 
    { 
        private CompareInfo m_compareInfo;
        public static readonly Comparer Default = new Comparer(CultureInfo.CurrentCulture);
        public static readonly Comparer DefaultInvariant = new Comparer(CultureInfo.InvariantCulture);
 
        private const String CompareInfoName = "CompareInfo";
 
        private Comparer() { 
            m_compareInfo = null;
        } 

        public Comparer(CultureInfo culture) {
            if (culture==null) {
                throw new ArgumentNullException("culture"); 
            }
            Contract.EndContractBlock(); 
            m_compareInfo = culture.CompareInfo; 
        }
 
        //private Comparer(SerializationInfo info, StreamingContext context) {
        //    m_compareInfo = null;
        //    SerializationInfoEnumerator enumerator = info.GetEnumerator();
        //    while( enumerator.MoveNext()) { 
        //        switch( enumerator.Name) {
        //            case CompareInfoName: 
        //                m_compareInfo = (CompareInfo) info.GetValue(CompareInfoName, typeof(CompareInfo)); 
        //                break;
        //        } 
        //    }
        //}

        // Compares two Objects by calling CompareTo.  If a == 
        // b,0 is returned.  If a implements
        // IComparable, a.CompareTo(b) is returned.  If a 
        // doesn't implement IComparable and b does, 
        // -(b.CompareTo(a)) is returned, otherwise an
        // exception is thrown. 
        //
        public int Compare(Object a, Object b) {
            if (a == b) return 0;
            if (a == null) return -1; 
            if (b == null) return 1;
            if (m_compareInfo != null) { 
                String sa = a as String; 
                String sb = b as String;
                if (sa != null && sb != null) 
                    return m_compareInfo.Compare(sa, sb);
            }

            IComparable ia = a as IComparable; 
            if (ia != null)
                return ia.CompareTo(b); 
 
            IComparable ib = b as IComparable;
            if (ib != null) 
                return -ib.CompareTo(a);

            throw new ArgumentException("Argument_ImplementIComparable");
        } 

        //[System.Security.SecurityCritical]  // auto-generated_required 
        //public void GetObjectData(SerializationInfo info, StreamingContext context) { 
        //    if (info==null) {
        //        throw new ArgumentNullException("info"); 
        //    }
        //    Contract.EndContractBlock();

        //    if( m_compareInfo != null) { 
        //        info.AddValue(CompareInfoName, m_compareInfo);
        //    } 
        //} 
    }
} 
